Refrigerator embodying stabilized mixtures of oil and aliphatic halides



Patented Apr. 24, 1951 REFRIGERATOR EMBODYING STABI- LIZED MIXTURES OFOIL AND ALI- PHATIC HALIDES Leonard 0. Flowers, Longmeadow, Mass,assignor to Westinghouse Electric Corporation, East Pittsburgh, Pa., acorporation of Pennsylvania No Drawing. Application February 3, 1950,Serial No. 142,341

4 Claims. 1

This invention relates to mechanical refrigerators embodying analiphatic halide refrigerant medium and a petroleum oil lubricant incombination with a stabilizing additive.

It has been found that a mixture of halogenated aliphatic compound andpetroleum oil, particularly as used in a mechanical refrigerator, issubject to a deteriorative reaction, particularly pronounced whensubjected to heating during compression. Even though the system has beendried exhaustively to remove any possible traces of moisture, it hasbeen found that the mixture will react to produce sludge, gums, and theso-called copper-plating wherein copper from the copper tubing, copperconductors and other copper members of the refrigerator are deposited onsteel or other metallic parts. As the mixture of petroleum lubricant andthe refrigerant is subjected to still higher temperatures, a charring ofthe oil will occur. Other undesirable reactions take place as will beset forth hereinafter. Tests with previously suggested additives forrefrigerants have shown that they are not particularly effective sincemost of such additives simply absorb excessive moisture and react withfree acids. However, at high temperatures, the mixture is reactive inthe refrigerator systems to produce the undesirable results recited.

The object of this invention is to provide a stabilized mixture ofpetroleum oil, and a halogenated aliphatic refrigerant.

A further object of the invention is to provide for introducing into asealed refrigerator system containing the halogenated aliphaticrefrigerant and petroleum oil a small amount of boric anhydride.

Another object of the invention is to provide a refrigerator comprisinga sealed system wherein a mixture of halogenated aliphatic refrigerantand a lubricating oil is in contact with boric anhydride as astabilizer.

Other objects of th invention will in part be obvious and will in partappear hereinafter. For a better understanding of the nature and objectsof the invention, reference should be had to the following detaileddescription.

It has been discovered that boric anhydride produces an unexpectedstabilizing effect when it is placed in contact with a mixture ofhalogenated aliphatic refrigerant and petroleum oil lubricant, allenclosed within a sealed refrigerator system. Mechanical refrigeratorsare commonly constructed with a sealed system including a compressorcomposed of an electric motor having copper wire windings, steel shaftsand compressor parts, tubing or the equivalent comprising a condenserWhere the compressed vapors or refrigerant liquefy, a capillary tube oran expansion valve or the like controlling the flow of liquidrefrigerant, and an evaporator in which the liquid refrigerant vaporizesand thereby produces cooling. The vapor of the refrigerant passes overthe motor and its copper windings thereby cooling them. In thecompressor, the refrigerant vapors are compressed thereby becominghighly heated. The refrigerant possesses no substantial lubricatingcharacteristics and it is necessary to have present a small amount ofoil which is entrapped or carried by the apors of refrigerant to themoving parts of the compressor and motor to provide for lubricating thebearing surfaces. The coppering effect has been found to occur withinsuch a system because of some reaction whose mechanism is not completelyknown. It causes copper to be carried over from some of the windings ofthe motor and plated on the steel parts. In some cases, coppering canextend to the metallic bearing parts of the compressor so as to causebearing failures and may reach the capillary tube wherein the expansionof the fluid refrigerant is controlled. A sludge or gum may be producedby reaction between the petroleum oil and the aliphatic haliderefrigerant particularly at elevated temperatures of above C. Sludge canclog the capillary tube and thereby cause improper functioning of therefrigerator.

Heretofore, the sealed systems were charged with petroleum oil andaliphatic halide refrigerants dried to predetermined extent to preventthe freezing of small amounts of water at critical points of the system.However, investigation indicates that minute amounts of water probablycause only slight corrosion. More highly improved and exhaustivedehydration processes have been put into operation so that normalhousehold refrigerators for instance very rarely suffer deteriorationfrom corrosion or copper plating, but it appears that the highly driedmixture of oil and refrigerant will char more rapidly at elevatedtemperatures. More recently, it has been discovered that highercompressor temperatures which are necessitated under some conditionscause a reaction to occur between the aliphatic halide and petroleumoil, even within a highly water freed system, whereby a deteriorativereaction occurs resulting in sludging and eventual charring of th oil aswell as including the coppering effect.

In accordance with this invention, an amount of boric anhydride or boronoxide (B203) is disposed within the sealed system in contact with themixture of petroleum oil and aliphatic halide refrigerant. The boricanhydride may be in the form of a fused lump or other shape fastened tothe walls of the system or it may comprise pellets mother-particlesdisposed within aporous casing or cartridge permeable to the. liquid; Aslittle boric anhydride as, 0.01% of the weight of the mixture ofrefrigerant and petroleum oil has:

some benefit. However, it is recommended that larger amounts of theorder of 1% and higher of: boric anhydride be employed to insure the'most efficient results. Thus acids produced by decomposition of thealiphatichalide may react with theboric anhydride and' deplete it.Consequently, a substantial amount of the boric an refrigerant carryingsmall amounts of the oil or in the liquefield refrigerant coming from.the condenser. There is no upper limit on the amount of the boricanhydride or the number of places atv which it may be located.

Orthoboric acid (H3Bo3). has been tried in the same manner as the boric:anhydride with: some benefit, but boric acid is not as effective asboric anhydride.

The following examples illustrate the benefits of the present invention.A mixture of approximately 50% by volume'ofa refrgerator petroleumlubricating oil and 50% by volume of dichlorodifluoromethane wasprepared. The mineral oil was a highly refined naphthene oil having.aviscosity of 1-50 seconds Saybolt at 100F. The

mixture was dried to remove all traces of moisture.v

and other undesirable impurities. The mixturebe in pellets or otherlarge particles that may be retained in place to prevent their beingcaught and transported to the capillaries where they may cause: damage.

Since certain obvious changes may be made in the above procedure anddifferent embodiments of the invention could be made without departingfrom the scope thereof, it is intended that all matter contained in theabove description shall be interpreted as illustrative and not in alimiting sense..

I claim as my, invention:

1. In a' refrigerator comprising a sealed system including a compressor,in combination, a

supply of. refrigerant medium disposed in the sealed; system wherebyvapors of the refrigerant medium. are compressed in the compressor andcondensed to a liquid, the refrigerant medium comprising a halogenatedaliphatic compound, a petroleum oil for lubricating the compressor inadmixture with the refrigerant medium, the mixture of petroleum oil andhalogenated aliphatic compound being subject to deteriorative reactioninthe system when heated by compression, and boric anhydride disposed inthe system in contact with the mixtureof petroleum oil and refrigerantmedium toreduce deteriorative retem including a compressor, incombination, a.

, supply of refrigerant medium disposed in the may beput in contact-withsteel and copper wire at room temperature up to about 100 C.with-' outexhibiting any undesirable deterioration. However, when heated to atemperature of 175 C., the mixture became progressively darker, turningyellow in two days and eventually turning black and opaque within 60days with con-- siderable'sludge formed. The copper wire was etched anda copper colored deposit appeared on the steel- 'At the end of theperiod, charring of theoilwas observed.

Another sealed system was prepared duplicating the former but containing1%" by weight, based on the weight of the refrigerant oil mixture, offusedboric anhydride in the form of small pellets. The latter system washeated at a temperature of 175 C. for 450 days. At the end' of thisperiod, the color of the mixture had darkened very slightlyfcomparableto the condition of the first system at the end of thesecond day. Therewas no observable sludge, no etching of the coppeer and no copperydeposit on the steel in thesecond system.

The refrigerant medium may comprise one or more aliphatic halidesormixtures embodying'the aliphatic halides as the major component. Theremay be disposed dehydrating agents or other additives in the refrigerantas is well known. Chlorofiuoromethanes are the preferred refrigjerant.The petroleum oil'may comprise paraffin base or naphthene base oils orother known hydrocarbon lubricants. V

The boric anhydride is ordinarily secured by fusing boric acid at anelevated temperature. However, it maybe secured by other processes andis well known as such. For the purpose of this. invention, it isdesirable, that the boric anhydride.

"1 sealedsystem whereby vapors of the refrigerant medium are compressedin the compressor and condensed to a liquid, the refrigerant mediumcomprising a halogenated aliphatic compound, a petroleum oil forlubricating the compressor in admixture with the refrigerant medium, themix-, ture of petroleum oil and halogenated aliphaticposed in the systemin contact with the mixture of petroleum oil and refrigerant mediumtoreduce deteriorative reaction.

4. In a refrigerator comprising a sealed system including a compressor,in combination, a supply of refrigerant medium disposed in thesealedsystem whereby vapors of the refrigerant medium are compressed in thecompressor and V condensed to a liquid, the refrigerant mediumcomprising a halogenated aliphatic compound,

a petroleum oil for lubricating the compressor in admixture withthe'refrigerant medium, the mixture of petroleum oil and halogenatedaliphatic compound being'subject to deteriorative reaction in the systemwhen. heated by compresi REFERENCES CITED The following references areofrecord in. the file: of this patent UNITED STATES PATENTS Number NameDate 2,212,8 26 Downing. Aug. 27,, 1940 2,523,863 Cooket al Sept. 26,1950

1. IN A REFRIGERATOR COMPRISING A SEALED SYSTEM INCLUDING A COMPRESSOR,IN COMBINATION, A SUPPLY OF REFRIGERANT MEDIUM DISPOSED IN THE SEALEDSYSTEM WHEREBY VAPORS OF THE REFRIGERANT MEDIUM ARE COMPRESSED DIN THECOMPRESSOR AND CONDENSED TO A LIQUID, THE REFRIGERANT MEDIUM COMPRISINGA HALOGENATED ALIPHATIC COMPOUND, A PETROLEUM OIL FOR LUBRICATING THECOMPRESSOR IN ADMIXTURE WITH THE REFRIGERANT MEDIUM, THE MIXTURE OFPETROLEUM OIL AND HALOGENATED ALIPHATIC COMPOUND BEING SUBJECT TODETERIORATIVE REACTION IN THE SYSTEM WHEN HEATED BY COMPRESSION, ANDBORIC ANHYDRIDE DISPOSED IN THE SYSTEM IN CONTACT WITH THE MIXTURE OFPETROLEUM OIL AND REFRIGERANT MEDIUM TO REDUCE DETERIORATIVE REACTION.